Improvement in parallel rulers



v Jun-1.1.1.! M-l-J1.L-IJU a. Rama .1. UL I. LUJIL- JOSEPH GARDAM. OFBROOKLYN, NEW YORK.

IMPROVEMENT IN PARALLEL RULERS.

Specification forming part of Letters Patent No. 192,16 1, dated June19, 1877 application filed May 9, 1877.

To all whom it may cancer-n:

Be it known that I, JOSEPH GARDAM, of Brooklyn, in the county of Kingsand State of New York, have invented a new and useful Improvement inParallel Rulers, which improvement is fully set forth in the followingspecification and accompanying drawing, in which- Figure 1 and Fig. 2illustrate the plan and end view of my proportional parallel rule, Fig.3 and Fig. 4 being respectively an enlarged plan and vertical transversesection through line J J.

The object of my invention is to furnish an instrument for draftsmenwhich shall meet the requirements of the T-square and scale combined, asalso enabling the draftsman to accurately draw any number of lines tothe inch, without preparatorily dividing said inch to the'number of,lines therein to be drawn.

The instrument consists of a protra'ctor, P, preferably cast to a guidepiece or slide, 1? sliding in a recessed frame, F, held to thedrawing-board by lugs Z and screws Y, said protractorP having a-limb orblade, B, turning on its center N, and clamped to the graduations of theprotractor P by means of vendorclamp N An additional guide piece orslide H, more clearly shown in plan, Fig. 3, is placed in frame F, andconnected to lever L by the travelingpivot X lever L being connected toprotractor P by movable link L on pivots X and X Slides P and H arefurnished with triangular cavities, in which are mounted centerpins 0,designed to support the toggles or keys T and T and so placed as not topermit of the insertion of toggles or keys T and T except it be at anangle either above or below the center lines J J and J J The springs Aand A, are provided to insure the constant contact of the toggle or keyedges plied with indices I, traveling with the protractor P over eitherscales G, and consequently showing the absolute amount of movement onthe part of blade B.

In using theinstrument apply the left-hand thumb and forefinger to leverL, the stroke length of which is governed by an index-stop clamped toits corresponding graduations by screw S. It will now be evident that ifthe toggles or keys T and T are placed over their pins 0, with theirwards parallel and below their corresponding center lilies J J and J J apressure on the leverL in the direction of the arrow will cause slide Hto move in the same direction, but by the retrogression of lever L thetoggle or key T is caused! to jamb on the inner face of frame F, therebyholding slide H in position, and subsequently causing a movement ofslide P protractor P, and blade B in the direction of the arrow. Theeventual amount of movement of blade B produced by a full action ofleverL is, therefore, an amount equal to that indicated by the indexstop at Son its corresponding graduations. A successive number of movements onthe part of lever L will, therefore, give any desired number of linesseparated by equal distances.

By placing the wards of the toggles or keys above their center lines, amovement of blade B in the opposite direction is obtained, and byplacing the wards in opposite directions the instrument becomes fixed.

In using the instrument as an ordinary T- square, displace one of thetoggles and turn the other so as to escape the inner face of frame F.

Having thus described my invention, what I claim, and desire to secureby Letters Patent is- 1 A guided protraotor with movable blade propelledby a linked lever, in conjunction with two toggles or keys, to producethe parallel motion of the blade, substantially as shown and described.

2. The graduated indexstop S, as required for the purpose set forth.

3. The combination of the springs V V with the frame F, for the purposeof supporting scales of either trapezoidal or triangular section,substantially as specified.

JOSEPH GARDAM.

Witnesses:

-J. G. FREEMAN,

J. 0. SEBALD.

